If you haven't heard these arguments before, it's clearly because you've never read any of the discussions attached to our climate articles. One or more of these statements appear in just about every single climate article we run, which is made even more disappointing by the fact that these arguments are ludicrously, laughably wrong. People should be embarrassed to be making them (although I'd imagine most are oblivious to that fact). In an attempt to forestall further public humiliation, I'm going to explain why, exactly, they're such terrible arguments.

“The warming is just part of a natural cycle”

Is this a natural cycle? The most important thing to note here is that cycles imply something... well, cyclical. As in things go up, but come back down again. A look at the temperature records of the last century-plus shows that this is exactly what is not happening. Temperatures go up and flatten out at times, but they never go back down. More specifically, next month, it will be 20 years since the last time we had a month where the global temperature was below last century's average.

The other reason that this is a nonsensical argument is that natural cycles aren't some sort of magic—like anthropogenic factors, they influence the climate for physical reasons. In other words, if something natural is heating the atmosphere, we should see some indication of it: a change in the amount of sunlight reaching the earth, a large pool of warm water at the ocean's surface, or something similar. Just saying "natural" doesn't get you a free pass out of physics, and we haven't seen anything physical that could possibly be causing the warming—nothing other than added CO2.

“We’ve been warming up since the last ice age”

OK, so maybe there's something very subtle and longer-term going on around here. Which takes us to the second argument: we've been warming up since the end of the last ice age. That's wrong from the perspective of what we know about how ice ages work. Ice ages are driven by changes in the amount and distribution of sunlight over the surface of the Earth, caused by regular variations in our planet's orbit and axis of rotation. Since these things are so regular, we can also calculate exactly when and to what degree these changes should be influencing temperatures.

This warming influence peaked over 5,000 years ago. Based on orbital mechanics alone, we should have been slowly cooling off for thousands of years.

If you look at materials that capture indications of past temperatures, that's exactly what you see. Our planet has been cooling for thousands of years—the exact opposite of what people are claiming.

Guess what? The Earth has been getting cooler for thousands of years. Taken from Marcotte et. al.

The other thing worth noting about these orbital cycles: on their own, they don't really change the energy balance of the Earth all that much. The temperature impact they should have is much smaller than the swings we see as the Earth enters and exits glacial periods. How do they get exaggerated? By greenhouse gasses, primarily carbon dioxide.

“To think humanity can influence the climate is pure arrogance”

Which takes us to the argument that there's no possible way for humanity to influence the climate. Which, again, is simply magical thinking. We know as a matter of basic physics that carbon dioxide can warm the planet. We know that, in our planet's past, it has warmed the planet (Google the PETM if you have any doubts). Do people honestly think that if humanity puts the carbon there instead, it somehow won't count?

Even if you want to ignore carbon dioxide, the argument doesn't make any sense, given that people are seriously examining the prospect of altering the climate using geoengineering. Although some of the ideas—like orbital Sun-shades—are a bit on the edge of science fiction, others—like injecting reflective aerosols into the stratosphere—could probably be tested next year if we really wanted to. It's not arrogance to think we have the ability to alter the climate; it's reality.

There is really nothing sensible about any of these arguments. They're bad, and if you use them, you should stop immediately. If you use them at Ars, you should feel bad.

Listing image by Aurich Lawson/Ars Technica

Promoted Comments

Apparently, I didn't make something as clear as i could have about the "natural cycles", so I'll give this another try:

We know of lots of short-term cycles, like ENSO and the PDO. Those are clearly not causing the warming, given that there's no indication of cycling in the short-term record, as shown in the first graph.

We know of a significant long-term cycle, the one that drives the entry and exit into glacial periods. We low the warming isn't caused by that, because the orbital forcings peaked over 5,000 years ago, and the temperatures have been declining since then, as shown in the second graph. (The second graph comes from the Marcotte paper, and what matters in it for this argument is not the recent uptick; it's the fact that temperatures had been declining for the last 5,000 years.)

Could it be possible that there's some intermediate natural cycle, one that operates on a mult- century scale? Sure, it's possible. But if one existed, it would be warming the atmosphere through some physical process that we can detect. We don't detect any such thing. So, to make this argument, you have to posit that there's both a cycle we've never detected, and it's influencing the atmosphere through physics that we've not been able to detect.

Given the extensive amount of time we've spent looking at things, missing both of those is implausible. And, given that something is changing that could explain both the warming and the pattern of warming - meaning rising CO2 levels - then to favor some completely mysterious "natural cycle" involves leaving scientific reasoning behind.